The natural intervertebral disc contains a jelly-like nucleus pulposus surrounded by a fibrous annulus fibrosus. Under an axial load, the nucleus pulposus compresses and radially transfers that load to the annulus fibrosus. The laminated nature of the annulus fibrosus provides it with a high tensile strength and so allows it to expand radially in response to this transferred load.
In a healthy intervertebral disc, cells within the nucleus pulposus produce an extracellular matrix (ECM) containing a high percentage of proteoglycans. These proteoglycans contained sulfated functional groups that retain water, thereby providing the nucleus pulposus within its cushioning qualities. These nucleus pulposus cells may also secrete small amounts of cytokines as well as matrix metalloproteinases (“MMPs”). These cytokines and MMPs help regulate the metabolism of the nucleus pulposus cells.
In some instances of disc degeneration disease (DDD), gradual degeneration of the intervertebral disc is caused by mechanical instabilities in other portions of the spine. In these instances, increased loads and pressures on the nucleus pulposus cause the cells to emit larger than normal amounts of the above-mentioned cytokines. In other instances of DDD, genetic factors, such as programmed cell death, or apoptosis can also cause the cells within the nucleus pulposus to emit toxic amounts of these cytokines and MMPs. In some instances, the pumping action of the disc may malfunction (due to, for example, a decrease in the proteoglycan concentration within the nucleus pulposus), thereby retarding the flow of nutrients into the disc as well as the flow of waste products out of the disc. This reduced capacity to eliminate waste may result in the accumulation of high levels of toxins.
As DDD progresses, the toxic levels of the cytokines present in the nucleus pulposus begin to degrade the extracellular matrix (in particular, the MMPs (under mediation by the cytokines) begin cleaving the water-retaining portions of the proteoglycans, thereby reducing its water-retaining capabilities). This degradation leads to a less flexible nucleus pulposus, and so changes the load pattern within the disc, thereby possibly causing delamination of the annulus fibrosus. These changes cause more mechanical instability, thereby causing the cells to emit even more cytokines, thereby upregulating MMPs. As this destructive cascade continues and DDD further progresses, the disc begins to bulge (“a herniated disc”), and then ultimately ruptures, causing the nucleus pulposus to contact the spinal cord and produce pain.
Olmarker, Spine 26(8), 2001, pp. 863-9(“Olmarker I”) and Aoki, Spine 27(15), 2002, pp. 1614-17 teach that TNF-α appears to play a role in producing the pain associated with the nucleus pulposus contacting nerve roots of the spinal cord.
US Published Patent Application No. US 2003/0039651 (“Olmarker II”) teaches a therapeutic treatment of nerve disorders comprising administration of a therapeutically effective dosage of at least two substances selected from the group consisting of TNF inhibitors (both specific and non-specific), IL-1 inhibitors, IL-6 inhibitors, IL-8 inhibitors, FAS inhibitors, FAS ligand inhibitors, and IFN-gamma inhibitors.
In the examples of Olmarker II, Olmarker II further teaches that these substances are to be administered through systemic pathways. In particular, Olmarker II teaches that “the major contribution of TNF-alpha may be derived from recruited, aggregated and maybe even extravasated leukocytes, and that successful pharmacologic block may be achieved only by systemic treatment. [0133]. Of note, Olmarker II appears to discourage the local addition of one therapeutic agent (doxycycline) to a transplanted nucleus pulposus. [0128].
PCT Published Patent Application No. WO 02/100387 (“Olmarker III”) teaches the prevention of neovasculariation and/or neo-innervation of intervertebral discs by the administration of anti-angiogenic substances. Again, however, Olmarker III teaches systemic administration of these therapeutic agents.
U.S. Pat. No. 6,419,944 (“Tobinick”) discloses treating herniated discs with cytokine antagonists, including infliximab. However, Tobinick teaches that local administration involves a subcutaneous injection near the spinal cord. Accordingly, Tobinick does not teach a procedure involving a sustained delivery of a drug for the treatment of DDD, nor directly administering a specific cytokine antagonist (such as infliximab) into the disc.
US Published Patent Application No. 2003/0049256 (Tobinick II) discloses that injection of such therapeutic molecules to the anatomic area adjacent to the spine is accomplished by interspinous injection, and preferably is accomplished by injection through the skin in the anatomic area between two adjacent spinous processes of the vertebral column.
Tobinick II further teaches that TNF antagonists may be administered by interspinous injection in the human and that the dosage level is in the range of 1 mg to 300 mg per dose, with dosage intervals as short as two days. Tobinick II further discloses that Interleukin-1 antagonists are administered in a therapeutically effective dose, which will generally be 10 mg to 200 mg per dose, and their dosage interval will be as short as once daily.
Tobinick, Swiss Med. Weekly, 2003, 133, 170-77 (“Tobinick III”) teaches both perispinal and epidural administration of TNF inhibitors for spine related therapies.
Karppinen, Spine, 28(8), 203, pp. 750-4, teaches intravenously injecting or orally administering infliximab into patients suffering from sciatica.
As with Tobinick I and II, Karppinen does not teach a procedure involving a sustained delivery of a drug for the treatment of DDD, nor directly administering a specific cytokine antagonist (such as infliximab) into the disc.
U.S. Pat. No. 6,352,557 (Ferree) teaches adding therapeutic substances such as anti-inflammatory medications to morselized extra-cellular matrix, and injecting that combination into an interverterbral disc.
However many anti-inflammatory agents are non-specific and therefore may produce unwanted side effects upon other cells, proteins and tissue. In addition, the pain-reducing effect of these agents is typically only temporary. Lastly, these agents typically only relieve pain, and are neither curative nor restorative.
Alini, Eur. Spine J. 11(Supp. 2), 2002, pp. S215-220, teaches therapies for early stage DDD, including injection of inhibitors of proteolytic enzymes or biological factors that stimulate cell metabolic activity (i.e., growth factors) in order to slow down the degenerative process. Alini I does not disclose inhibiting growth factors.
US Published Patent Application US 2002/0026244 (“Trieu”) discloses an intervertebral disc nucleus comprising a hydrogel that may deliver desired pharmacological agents. Trieu teaches that these pharmacological agents may include growth factors such as TGF-B and anti-inflammatory drugs, including steroids. Trieu further teaches that these pharmacological agents may be dispersed within the hydrogel having an appropriate level of porosity to release the pharmacological agent at a desired rate. Trieu teaches that these agents may be released upon cyclic loading or upon resorption.
Takegami, Spine, 27(12), 2002, 1318-25 teaches that injecting TGF-B into the disc space results in enhanced replenishment of the extracellular matrix damaged by cytokines. Takegami further teaches that the half-life of a growth factor injected into the interverterbral disc can be expected to be longer than that injected into a synovial joint because the nucleus pulposus is surrounded by the fibrous structure of the annulus fibrosus, thus providing a confined environment. Diwan, Tissue Engineering in Orthopedic Surgery, 31(3) July 2000, pp. 453-464, reports on another Takegami paper that concluded that a delivery system allowing prolonged delivery (>3 days) would have to be used to obtain the observed effect of the growth factor.
Alini, Spine 2003 28(5), pp. 446-54, discloses a cell seeded collagen-hyaluronan scaffold supplemented with growth factors such as TGF-B, bFGF, and IGF-1 for use in regenerating a nucleus pulposus.
Maeda et al. Spine 2000, 25(20 pp. 166-169, 2000 reports on the in vitro response to interleukin-1 receptor antagonist protein (IRAP) of rabbit annulus fibrosus exposed to IL-1. Maeda suggests that IRAP could be useful in inhibiting the degradation of the disc.
Yabuki, Spine, 2001, 26(8), 870-5, teaches the use of an anti-TNF drug for the treatment of sciatica.
U.S. Pat. No. 6,277,969 (“Le”) discloses the use of anti-TNF antibodies for therapy of TNF-mediated pathologies. Le teaches parental administration of the antibodies.
In sum, when investigators suggest the administration of specific TNF-a inhibitors or specific interleukin inhibitors, the investigators appear not only to teach only the administration of those therapeutics to tissue outside the disc, but it also appears to discourage the trans-discal administration of therapeutic substances.